A coordinate measuring method with two operation modes, based on the adjustable articulated arms, is proposed to keep measurement capability in global space and improve the measurement precision in local space. The adjustable articulated arm coordinate measuring machine (AACMM) with an electromagnetic locking device can automatically switch between the all-free articulated arms operation mode and the partially bound articulated arms operation mode. In the former mode, three arms and six articulations can freely move and measure the coordinates of any point in global space. In the latter mode, the front two articulations are locked to improve the measurement precision by decreasing the importation of angle errors in the local space. A prototype of the adjustable AACMM has also been designed and developed. A mathematical model for the adjustable AACMM has been built. Theoretical analysis and numerical simulation show that the partially bound AACMM performed much better than the all-free AACMM in single point repeatability and length measurement precision in the local space. Therefore, the proposed coordinate measuring method based on the adjustable articulated arms is verified as being effective.
A method is introduced for calibrating the kinematic parameters of articulated arm coordinate measurement machines (AACMM) to improve its accuracy. The kinematic model of AACMM is firstly built according to Denavit-Hartenberg method. Then specific kinematic parameters and the errors of which are analyzed. A nonlinear programming genetic algorithm is adopted to seek the global optimal solution of the kinematic parameters. Computation result indicates that the method can be used to implement the calibration precisely and quickly.
Interferometry is one of the effective approaches for characterizing dispersive optical components. The foundation is
partial coherence theory. A derivation of partial coherence theory relating to the characterization of dispersive medium is
presented here by combining with the measurement of CFBG (Chirped Fiber Bragg Grating), a dispersive fiber optic
component with wide application in the compensation of the dispersion in optical telecommunication system. In the
derivation the dispersion property, generally neglected in conventional partial coherence theory, is taken into account. It
will make sense for instructing the measurement, research and investigation employing interferometric system in which
dispersive medium is involved.
KEYWORDS: Error analysis, Data modeling, Teeth, Information science, Information technology, Precision measurement, Fluctuations and noise, Lutetium, Current controlled current source, Spherical lenses
Helicoidal surfaces are very useful in many aspects, their error assessment has become more and more important. In this
paper, studied the method of the error assessment, and the key point was focused on how much number of measuring
points to be enough. Firstly, the current methods of the error assessment were analyzed. Then, the study was spread out
from general equation of the helicoidal surfaces to general model of the error and the error assessment, and pointed out
the number of the measuring points could be determined with the variations of the means and the variances of the errors.
Finally, took a worm as an example to explain that the method is feasible.
Involute helicoid is widely used in engineering and its accurate measurement is a focused research subject for improving
its application. The analytic representation of involute helicoid under Cartesian coordinate system is established
according to its formation principle. The surface error model for assessing the profile error of involute helicoid is
discussed according to differential geometry characteristic. Finally a practical measurement of an involute worm is
conducted with a coordinate measuring machine and the surface profile error evaluation is provided according to the
surface error model for validating the feasibility and practicability thereof.
Analyzes the interferogram of a system for measuring the dispersion of CFBGs (chirped fiber Bragg grating) through
Fourier spectrometric method. Theoretical representation of the interferogram is provided. A numerical model for
simulating the interferogram is established under the common cognition that the recorded interfogram during the
scanning of OPD (optical path difference) along the light beam axis is the sum of separate symmetrical interferogram of
all quasi-monochromatic light components according to power. This analysis method will facilitate the analysis of
interferogram of several interferometric systems in which the light transmits via a dispersive medium.
A novel high accuracy form error optical measurement system based on reflective intensity modulation optical fiber
sensor is presented. Combing the optical fiber sensor technology and optical fiber communication technology, the system
is developed by using optical switch to realize the Time Division Multiplex (TMD) of optical fiber sensing array,
improve the system efficiency, reduce cost and suppress errors caused by the movement of optical fiber. SNR (signal
noise ratio) and accuracy of the system are enhanced through lock-in amplifier. The intensity fluctuation of the reference
light is adopted to correct the effects of the power variation of light source and so as to improve stability of the system.
The experiment results show that the resolution of the system is up to 0.1μm and repeatability is about 0.5%. The
architecture of the system is very simple that it can be used in multiple form error measurement of mechanical parts of
different shapes by changing the number and layout of the optical fiber sensor array flexibly.
Introduces a Fourier transform spectrometric method for the precise characterization of dispersion of chirped FBGs(fiber
Bragg grating). The measurement system is a fiber Michelson interferometer composed of a broadband EDFA (Erium
doped fiber amplifier) light source, a 3db 2×2 fiber coupler, a pair of polarization controllers, a optical attenuator, a fiber
filter, an O/E converter, A/D converter, computer and a optical path difference (OPD) scanning system. The digital
interferogram of the system is acquired by recording the electric signal produced by the O/E converter through the A/D
converter and by computer during the scanning of OPD. The recorded interferogram is then manipulated through a
process involving low-pass filtering, fast Fourier transformation, phase unwrapping and computation of the numerical
differentials of the unwrapped phase to the wavelength so as to obtain the relative group delay of the chirped FBG under
test. It is proved by practical experiments that the repeatability of the system is up to Ps(picosecond) magnitude order.
Reports a laser diode alignment system for monitoring dam, building, bridge, etc. It comprises a light source and a
receiving unit. The former is mainly composed of a laser diode for emitting light in red spectrum band at wavelength of
680nm, a single mode fiber for spot transforming and mode selecting, and a reverse telescope for collimating the
emission light beam. The whole light source is mounted on a 4-dimension adjustable table fixed on a tripod. The latter is
an embedded computer based on PC104 architecture. It contains a mainboard, an image grabber, a LCD display and a
CCD. Central position of the light spot is calculated according to barycenter method. It is proved by experiments in lab
that within a span of 8m the direction stability of the alignment system is up to 1X10-6 magnitude order.
KEYWORDS: Data modeling, Error analysis, Data processing, Manufacturing, Information science, Information technology, Instrumentation control, Signal analysis, Artificial intelligence, Teeth
The measurement of helicoidal surfaces is very important for the manufacture and utilization of fine mechanical parts. It
usually employs the feature line error to represent the helicoidal surfaces' error. Two methods, commonly used to assess
the character line error, least-square method and accumulative sum method, are analyzed and compared here by
combining with practical data processing.
The measurement of helical surfaces is used not only to evaluate the precision of the surfaces, but also to analyze the sources of its deviation from the specification. In this article, many aspects of helical surfaces are contained, as the mathematical principle of forming the surface, the measuring equipment, the measuring methods and our research status. First the forming principle of the helical surface is given and the classification methods by the mathematical equations are shown. Then the equipment is summarized, and the classification and the working principles of the measurement of the helical surface is given. At third we introduce our research status, and also give a measurement example of a hobbing cutter and a concise analysis. From the analysis we derive a method to improve the quality of the helical surface. Finally, we discuss the future development of the measurement of the helical surface.
In this paper we propose a uniform mathematic model of helicoidal surfaces. We describe the spacing surface and the properties of helicoidal surfaces. We studie the description of real surfaces and on this basis, we derive the deviations from helicoidal surfaces and its uniform model. We provide an algorithm for the compensation of the stylus radius. This research is useful to unify the measurement of all kinds of helicoidal parts and to simplify the measuring procedures.
A single mode fiber (SMF) pigtailed laser diode alignment system used for coaxiality measurement of large scale holes is studied. The drift of angle of laser beam is restricted obviously by mode restriction of single mode fiber. The stability of laser reference line is the order of 1.5 x 10-6. It can be used in measurements of position and form errors of large scale workpieces.
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